1. Field of the Invention
The present invention relates to an information processing apparatus, more particularly, to an information processing apparatus suitable for suppressing storage of gaps caused by a difference in size of processing units for a video stream and an audio stream when these streams are coupled in digital broadcasting.
2. Description of the Related Art
The digital broadcasting for broadcasting programs digitally has been widely spread. A program in digital broadcasting further includes one or more programs. Each of the programs is exchanged by using a transport stream by MPEG (Moving Picture Expert Group) 2.
By the way, in digital broadcasting, different TV programs are broadcasted depending on time zones. Therefore, after a transport stream is converted to an elementary stream, one program must be switched to the next program in certain timing. Also in one program, a commercial (which is also a program) may have to be inserted during a main program. Splicing processing is needed for connecting elementary streams corresponding to the main program and the commercials when switching from one TV program to the other or switching from a TV program to a commercial.
Units (a video frame and an audio frame) for encoding a video stream and an audio stream, respectively multiplexed to an elementary stream are different time intervals from each other. FIG. 1 is a diagram for explaining a difference in length of a video stream and an audio stream included in a program. As shown in FIG. 1, one frame (video frame) of a video stream is 33 ms according to NTSC method. One frame (audio frame) of an audio stream is 24 ms. Therefore, even when the video frame of the video stream and the audio frame of the audio stream are synchronized at the beginning of the program, the timing of the second and following video frames and audio frames do not match. As a result, a time gap occurs.
Since the encoding unit is a frame, an appreciable gap highly possibly occurs at the ends of the video stream and of the audio stream at the end of a program of one TV program. In other words, the end of a frame of an audio stream is hardly located just at a splicing point of a video stream (a splicing point of video streams of different programs). That is, a gap may occur between the audio stream and the video stream.
As shown in FIG. 1, a video stream and an audio stream, which have a gap in time, are spliced in the last frame of a program. Then, in a program created by the splicing, the video frame and the audio frame may not be synchronized. As a result, by repeating splicing, gap amounts are accumulated, producing a larger gap amount gradually.